Whatever i do with my vehicles, i take photo copies & send it to the DVLA, registered post.
I have 2 vehicles that i only use for the summer, which i completed SORN for both, put them in the same envelope and sent them to the DVLA.
Woe & Behold, i got a £40 fine on one of my vehicles for not completing a SORN, which the DVLA have no record of receiving. Which i duly paid to avoid the fine from rising. HAve requested it back, when they check & correct their records, will not hold my breath
2 weeks ago, i received a fine for not taxing one of my trucks, so i duly photocopied the tax disc which is in date and sent it back, still waiting for a reply for that one.
My advice is, make sure you photo copy everything you send them, and keep the records for the time you own the vehicle.